Circular knitting machine with pneumatic thread feeding devices

ABSTRACT

A circular knitting machine for manufacturing open tubular fabric, having a fixed needle cylinder and rotatable cams and needles arranged along an arc portion of the needle cylinder and the remaining arc portion thereof free of needles, is equipped with pneumatic thread feeding devices arranged on a supporting structure rotatable around the needle cylinder. The devices each comprise a plurality of passages for respective threads, the passages converging towards a common exit and communicating with a source of compressed air blowing the threads towards the exit. The devices further include a plurality of levers each controlling a single thread and each being pivotable from a rest position in which it holds the corresponding thread retracted from the path of the needles into an operative position in which the thread projects from its passage into the needle path. The levers are selectively controlled when the feed device passes through the zone of the needle cylinder free of needles. Before this zone a cutting and clamping device is arranged which cuts the thread which has been knitted into a row regardless of whether the thread has to be changed or not.

United States Patent [191 Tenconi [451 June 24, 1975 1 CIRCULAR KNITTING MACHINE WITH PNEUMATIC THREAD FEEDING DEVICES [76] Inventor: Riccardo Tenconi, Via Tallera, 20,

Varese, Italy, 21100 221 Filed: Feb. 20, 1973 211 App], No.: 334,164

[52] US. Cl. 66/132 R; 66/140 R [51] Int. Cl. D04b 15/58; D04b 15/60 [58] Field of Search 66/132 R, 133, 134, 140 R,

66/144, 142, 145 R, 125 R, 19; 139/127 P Primary ExaminerW. C. Reynolds Assistant ExaminerA. M. Faik Attorney, Agent, or FirmDr. Guido Modiano; Dr. Albert Josif 57 ABSTRACT A circular knitting machine for manufacturing open tubular fabric, having a fixed needle cylinder and rotatable cams and needles arranged along an arc portion of the needle cylinder and the remaining are portion thereof free of needles, is equipped with pneumatic thread feeding devices arranged on a supporting structure rotatable around the needle cylinder. The devices each comprise a plurality of passages for respective threads, the passages converging towards a common exit and communicating with a source of compressed air blowing the threads towards the exit. The devices further include a plurality of levers each controlling a single thread and each being pivotable from a rest position in which it holds the corresponding thread retracted from the path of the needles into an operative position in which the thread projects from its passage into the needle path. The levers are selectively controlled when the feed device passes through the zone of the needle cylinder free of needles. Before this zone a cutting and clamping device is arranged which cuts the thread which has been knitted into a row regardless of whether the thread has to be changed or not.

1 Claim, 14 Drawing Figures PATENTEDJUN 24 I975 I SHEET CIRCULAR KNITTING MACHINE WITH PNEUMATIC THREAD FEEDING DEVICES The present invention relates to a circular knitting machine having pneumatic devices for selectively feeding the threads to the needles.

BACKGROUND OF THE INVENTION.

Generally in knitting machines the problem arises of feeding the needles forming the stitch with threads or yarns of various characteristics which succeed each other in the manufactured article according to a prede termined work programme. For this purpose the machines are provided with multiple feed devices which selectively bring these threads to the needles by means of suitable switching controls.

These feed devices must satisfy a series of require ments, which are absolute precision of intervention to ensure that a certain thread is fed to the needles instead of another, at the right point and without any possibility of error; the possibility of ensuring a sudden and at the same time precise changing of one thread with another; the possibility of guaranteeing that the precision of the interventions of these feed members is not at the expense of the working speed of the machine; the possibility of feeding a high number of alternative threads for each feed unit; and finally, in the case of machines of the multi-feed type, the possibility of limiting the zone of alternate introduction of the various threads supplied by a determined feed to a very small arc of the needle bed.

These problems, very much felt in knitting machines generally, become even more constraining in circular knitting machines, and more particularly in machines in which the needle cylinder is fixed while around it rotates a turntable carrying a plurality of feed devices, each with its own range of threads. Among these latter machines must be numbered those particular circular knitting machines designed for manufacturing open tubular fabric (open type), i.e. those machines in which the formation of the stitch takes place by rotation of the feed device in a single continuous direction and the article is knitted along an arc of the needle cylinder and not along the whole periphery thereof. In machines of this kind, the needles are arranged along an arc of the needle cylinder and the remaining circumferential arc of the needle cylinder is free of needles, thus defining a zone where the knitting terminates and a zone where the knitting newly initiates.

In these latter types of machine, each thread, supplied by a respective feed device which rotates about the general axis of the machine, is brought towards the needles at the beginning edge of the article, makes an almost complete row of stitches, emerges from the article at the other edge thereof and is cut, to be again taken up by the needles (either it itself or another thread which replaces it) at the next passage of the feed device through the zone where the knitting of the article initiates.

SUMMARY OF THE INVENTION The present invention offers a new solution to the problem of selectively feeding knitting machines, of the aforementioned type, with different threads by means of a device which because of its extreme structural simplicity, its low cost and absolute reliability of operation,

constitutes a preferred method in the field of knitting machines.

A further object of the invention is that said device consists of moving parts having very low inertia when in operation, because of which the control impulses originating from the general programme of the machine for introducing a thread into the article or for one thread with another have an instantaneous and thus rigorously exact response.

These and further objects which will be more evident hereinafter are attained by a circular knitting machine of the aforementioned type having pneumatic devices for selectively feeding the threads or yarns, which devices, moving relative to the machine meedles, each comprises a plurality of passages converging towards an exit adjacent to the needle bed, each occupied by a respective thread supplied from a stock of threads, and communicating with a pneumatic source arranged to send said threads towards said exit, and a corresponding plurality of control members for the respective threads mobile between a rest position in which they retain the thread, withdrawing it from the action of the pneumatic means, and a working position in which they bring the thread under the influence of said pneumatic means.

BRIEF DESCRIPTION OF THE DRAWINGS.

Further characteristics and advantages will be more evident from the description of some preferred but not exclusive embodiments of the invention, illustrated by way of non-limiting example in the accompanying drawings in which:

FIG. 1 is a partially sectional elevational diagrammatic view of a device for feeding threads to a circular knitting machine of the type for manufacturing open tubular fabric;

FIG. 2 is a diagrammatic plan view of the same device in the zone where the thread is cut and leaves the knitting zone;

FIG. 3 is a sectional view through the machine to an enlarged scale showing the operation of cutting the thread at its exit from the article;

FIG. 4 is a diagrammatic illustration of a first embodiment of that part of the device comprising the plurality of passages for the various threads to be selectively fed to the needles;

FIGS. 5 and 6 are diagrammatic lateral partly sectional views of one embodiment of the device in the working and rest position, respectively;

FIGS. 7 and 8 are views similar to those of FIGS. 5 and 6 of a different embodiment of the device;

FIG. 9 is a partly sectional elevation of a further em bodiment of the device, mounted on the knitting machine;

FIG. 10 is a sectional view of the device on a plane perpendicular to that of the preceding figure (line X-X of FIG. 9);

FIG. 11 is a diagrammatic plan view of the fixed cylinder and the rotatable turntable of a circular knitting machine to which the feed devices are applied;

FIGS. 12a, 12b, are diagrammatic illustrations of the development of the cylinder face between the zone where knitting terminates and the zone where knitting is initiated in three different positions of the feed units.

DESCRIPTION OF THE PREFERRED EMBODIMENT The cylinder of the machine is indicated schematically by the reference numeral 1, and on its periphery are disposed the knitting needles 2. These needles extend around a large part of the circumference of the cylinder, with the exception of an are A B (see FIG. 11), defining a zone of entry or commencement of the article, A, and a zone of exit or finish of the article, B. Around this cylinder 1, which is fixed, there rotates a turntable or support member 1a which carries the various feed devices and the spools of thread, not shown in FIG. 11. FIG. 1 shows one of these devices, 3, which selectively supplies a plurality of threads for knitting the article, each of the threads being unwound from a respective spool 4. Each of these devices 3 rotates in continuous movement about the cylinder 1, and, after one of the threads has been knitted in by the needles starting from the zone A of the cylinder, it supplies it to all the successive needles until it arrives at the zone B in which, at the end selvage of the article, a cutter having a fixed blade 5 and a movable blade 6 cuts the thread which has been knitted. The movable blade 6 is slidable within a groove of a fixed dial plate 6a of the machine and the fixed blade 5 is arranged on a block 5a secured to the dial plate 6a. A cutter of this type and employable for the kind of machine considered is disclosed in US. Pat. No. 3 640 094. Actuation of the movable blade 6 occurs by a cam rotatable above the dial plate 6a and controlling a butt of the movable blade, as described in the said US. Patent. After cutting of the knitted thread the device 3 continues to rotate and the same thread, or another if changeover has occured in the are between the zones A and B, is supplied to the first needles of the zone A.

The feed device 3 will now be described more specifically. This may consist, schematically, of a block 7 in which is formed a plurality of passages 8, which all converge towards a restricted face and join together at 9 in the immediate proximity of the needles. The passages 8 extend substantially radially to the needle cylinder 1. At the end opposite to the zone 9 the passages 8 are connected to a common duct 10 which is in communication by way of a tube 11 with a source of air under pressure. A thread 13 emerges into each of the ducts 8 through a tube 12, and upstream of this tube it passes through an element which operates at each change-over. Some embodiments of this element are shown in FIGS. 5 to 10.

Particular reference will now be made to FIGS. 5 and 6. In these figures each of the threads 13, which passes through a pair of guide eyelets l4 and 15, also passes through a further eyelet 16, which is between the other two and is supported by a lever 17 capable of oscillating about a pivot 18. The lever 17 is normally subjected to the traction action of a spring 19 which tends to maintain it in the rest position shown in FIG. 6. The said lever may be brought into the operative position shown in FIG. 5 by a thrust rod 20 connected to the mobile core of an electromagnet 21. The thread 13 further passes, upstream of the eyelet 14, through a pair of further eyelets 22 and 23, between which a disc brake 24 of known type, controlled electromagnetically, operates.

The operation of this first embodiment of the feed device is as follows:

It is firstly assumed that the thread which has just been knitted into a row is not to be changed for the next row. The said thread carried by the device 3 and delivered through the passage 8 has to be newly knitted by the needles starting from zone A and has a hanging end 13a, resulting from the cutting carried out by the cutting means 5, 6 on the thread just after the previous row has been terminated. During passage of the device 3 from the zone B to the zone A, the electromagnet 21 remains energized as it was during the entire preceding row and the jet of air through the duct 11 and passage 8 ensures that the thread projects from the thread guide by its appendix 13a, which is thus readily taken up by the first needles of the zone A to form the next row. If on the contrary the thread must be changed over in the article on exit from the zone B after the thread under consideration has been cut by the cutters 5, 6, the thread which ceases to be used must be withdrawn into its respective duct, whereas the new thread must in its turn be pushed out. The first thread is retracted by de-energizing the respective electromagnet 21 and then subjecting the lever 17 only to the return action of the spring 19, while simultaneously the brake discs of the device 24 which is now energized, clamp the thread. Consequently the thread can no longer be unwound from by its spool, and at the same time a loop 13b is formed. The thread no longer projects from its duct, and a new thread replaces the previous one, by an operation which is exactly opposite to that just described, i.e. the corresponding lever 17 is brought from the position shown in FIG. 6 to that shown in FIG. 5, subjecting the loop 13b to the action of the compressed air which causes the end 13a to emerge from the device 3 and approach the needles of the zone. In this latter case, however, it is not necessary to retract the lever 17 in the rest position.

As it is known, the changing of the yarn in these machines occurs in accordance with the working programme of the machine and the pattern of the article to be obtained. The thread which has been knitted into a row is always cut when it reaches the cutting means 5, 6 even if no change of the said thread has to occur.

It should be noted that the feed of compressed air to the ducts 8 may be continuous or may be limited only to the periods in which the device 3 passes in the range of zone A for feeding the threads to the needles which begin the knitting of the new row.

Naturally, taking into account the fact that each device carries a plurality of threads, each inserted into its own duct 8, each of the members described here are present in a device in a number equal to the number of threads, although for ease of representation only the members relative to one of these threads have been shown in FIGS. 5 and 6.

In the modification shown in FIGS. 7 and 8, the elements associated with each oscillating lever 17 (i.e. the electromagnetic elements which withdrawn the thread which ceases to be utilised from the zone of action of the needles) are replaced by a pneumatic control. In its simplest embodiment, each of the ducts 8, supplied from the source of compressed air 25 through the passage II, has a branch 26 which extends from a connector 27 also supplied from the source 25. The ducts 27, 28 extend in a direction which diverges from the direction of the duct 8. The other parts corresponding substantially to those shown in FIGS. 5 and 6, are indicated by the same reference numerals. The passage of compressed air through the ducts 11 and 27 is controlled alternately by solenoid valves 28 and 29. The operation of this modification is evident: if the solenoid valve 28 is kept open (and the solenoid valve 29 consequently closed) the thread 13 is subjected to the jet of air along the direction of the duct 8, and hence is arranged for feeding to the needles. If on the contrary the thread 13 ceases to be utilized, the solenoid valves 28 and 29 are switched over, because of which the thread becomes subjected (FIG. 8) only to the deviating action of the jet through the nozzle 27. The thread is thus deviated through the passage 26, to be again returned to the feed condition when the jet through the passage 27 is replaced by the main jet through the passage 11. In this case a disc brake 24 is also used to aid the operation of the device.

Reference will now be made to a further embodiment, shown in FIGS. 9 and 10, and substantially similar to that of FIGS. 5 and 6. The device comprises a block 107 which is mounted on the support structure 1a and rotates therewith. In FIG. 11 only twelve of such blocks 107 have been shown on the support structure but they are normally provided in a larger number, equal to that of the feeds of the machine. The said blocks 107 are arranged in place of the conventional thread feeding units provided on the machines considered. In each block 107 there is formed a plurality of converging ducts 108 which, starting from a common header 111, end into a common passage 109 through which the various threads which each occupy a respective passage 108, are selectively brought into the path of the needles. Each of the passages 108 also communicates, at the end most distant from the mouth 109, with the passage 112 through which the respective thread 113 passes. Each thread 113 traverses a pair of aligned holes 116 in the arms of a lever 117 pivoted about a fulcrum 118. Each lever 117 may pass from the working position shown in FIG. 9 by a continuous line to the rest position shown by a dotted line, under the action of a pusher 119 which may be activated by any suitable means, for example by electromagnetic control means 119a. Vice versa, each lever may be returned from the rest position to the working position by the action of a second pusher 120, also operable by any known means, for instance an electromagnetic control means 120a. As can be seen, in passing from the work position to the rest position, the thread 113 is partially retracted from the passage 108, to form with the help of a fixed stop 115, the loop 1l3-b which, when the lever 117 is again brought into the working position, ensures the immediate delivery of threads by the effect of the jet of compressed air which drags the free end of the thread out of the passage 109.

FIGS. 12a, 12b and 126 show the manner in which a thread is cut after knitting and subsequently fed to the needles of zone A.

FIG. 12a shows the thread while it is being cut. The feed device including block 107 has passed, during rotation of the support structure la, the cutting blades 5, 6, which are arranged on the stationary dial plate 6a. As it is known, in the machines which manufacture open tubular fabric, every thread fed to the machine is cut after it has been knitted by the needles to form a row and after the feed device has passed the zone B and reached the zone where no needles are more provided. The cutting occurs regardless whether the thread has to be changed or not.

The thread 113 which has been cut is retracted into its duct in the manner already described while the feed device continues to rotate supported by the support structure 1a and approaches to the zone A. The programme of the machines determines whether the thread which has just been cut has to be further used for another row or has to be changed.

Provided that a fabric having a stripe pattern has to be manufactured and the successive row has to be made of a different thread then the last row, a changing of the thread has to occur. According to the working programme the pusher corresponding to the said different thread is actuated to pivot the corresponding lever 117 into the operative position shown in FIG. 9 by a continuous line and the corresponding thread which has been numbered at 213, is blown out of passage 109 into the path of the needles, as shown in FIG. 120, for being knitted by the needles of zone A.

It will be understood that if the thread has not to be changed, the same thread which has been retracted (indicated at 113) will newly be caused to emerge from passage 109, as indicated at the feed device shown on the right in FIG. 12a. This occurs by operating the pusher 120 corresponding to this thread, while the other pushers 120 remain inoperative.

The above described operation continues by changing the threads or working with the same thread as described until the fabric having the said stripe pattern has been terminated.

It will be understood that the described operation is repeated for each feed device, that is for each feed of the machine.

The invention so conceived is susceptible to numerous modifications, all of which fall within the scope of the inventive idea. Furthermore all details may be replaced by others technically equivalent.

I claim:

1. In a circular knitting machine for manufacturing open tubular fabric having a fixed needle cylinder and cams rotatable around said needle cylinder, the needle cylinder having needles arranged along an arc thereof and a zone free of needles extending along the remain ing arc thereof, thread feed devices arranged rotatably around said needle cylinder and cutting means arranged for cutting the knitted thread at the end of said are provided with needles, said feed devices each comprising a plurality of passages directed towards the needle cylinder, a duct for supplying compressed air into said passages and means for selectively controlling feeding of said threads through said passages, said means including a plurality of levers in a number corresponding to the number of threads of each feed device and each having two spaced arms extending into the path of a respective thread and having eyelets for passing said thread therethrough, said levers being pivotable between a first position in which the respective thread is held in a rest position inside the corresponding passage withdrawn from the path of the needles and a second position in which the respective thread is held in an operative position projecting from said passages into the path of the needles, a fixed stop member arranged between said arms to form loops of the thread around said fixed stop member and said eyelets when the corresponding lever is in said first position, thereby retracting the thread from the path of the needles, and control means for selectively operating said levers in response to the working programme of the machine posite sides of their pivoting points and electromagnetical actuation means responsive to the working programme of the machine for controlling said pushers. 

1. In a circular knitting machine for manufacturing open tubular fabric having a fixed needle cylinder and cams rotatable around said needle cylinder, the needle cylinder having needles arranged along an arc thereof and a zone free of needles extending along the remaining arc thereof, thread feed devices arranged rotatably around said needle cylinder and cutting means arranged for cutting the knitted thread at the end of said arc provided with needles, said feed devices each comprising a plurality of passages directed towards the needle cylinder, a duct for supplying compressed air into said passages and means for selectively controlling feeding of said threads through said passages, said means including a plurality of levers in a number corresponding to the number of threads of each feed device and each having two spaced arms extending into the path of a respective thread and having eyelets for passing said thread therethrough, said levers being pivotable between a first position in which the respective thread is held in a rest position inside the corresponding passage withdrawn from the path of the needles and a second position in which the respective thread is held in an operative position projecting from said passages into the path of the needles, a fixed stop member arranged between said arms to form loops of the thread around said fixed stop member and said eyelets when the corresponding lever is in said first position, thereby retracting the thread from the path of the needles, and control means for selectively operating said levers in response to the working programme of the machine and the pattern of the article to be manufactured to pass from said first position into said second position or viceversa when said feed devices travel through said zone of the needle cylinder free of needles, said control means comprising pushers engaging said levers at opposite sides of their pivoting points and electromagnetical actuation means responsive to the working programme of the machine for controlling said pushers. 